The issue of imprisonment as a means to deter competition law offences is widely debated in doctrine. The purpose of this article is not to expound the ideas already mentioned in the legal literature on the advantages/disadvantages of such a sentence. This paper will focus on the question of whether imprisonment is a legitimate punishment to deter anti-competitive behaviours, regarding the theoretical, legal and/or practical difficulties encountered for a successful policy of European antitrust criminalization. To answer this question, the prison sentence issue against managers involved in cartel practices requires the application of a legitimacy test. Regarding this test, three conditions must be examined to legitimize the imprisonment of individuals responsible for an anticompetitive practice: the seriousness of the practice, the risk of type 1 error, and the social consensus on the seriousness of market violations.